Glow tube



J. A. VlcToREEN ET AL 2,728,004

Dec. 20, 1955 GLOW TUBE Filed NOV. 16, 1948 2 Sheets-Sheet l INVENTORSJOHN A. VIGTOREE/V JAMES H. EDDLESTON Dec. 20, 1955 J. A. VICTOREEN ETAL 2,728,004

GLOW TUBE 2 Sheets-Sheet 2 Filed Nov. 16, 1948 FIG. 2

JAMES H EDDLESTO/V United States Patent Q crow TUBE.

John A. Victoreeu and James H. Eddleston, Cleveland;

Ohio, assignors to The Victoreen Instrument Company, Cleveland, Ohio, atcompany of Ohio Application November 16, 1948, Serial No. 60,254 11'Claims. (Cl. 313-54) This invention relates to electron dischargedevices of gaseous conduction type andmore particularly to. the methodand apparatus foraffording a more exact striking voltage for theoperation of such tubes.

Heretofore, it has been common knowledge to provide gaseous conductiontubes which are utilized for a. great many purposes of which the mostcommon is for. voltage regulation. One of the most common defects ofsuch tubes was the fact thatv the striking or starting voltage needed tostart the operation was considerably higher than the voltage necessaryto maintain a state of ionization in. the tube. Although this was not aserious deficiency for a great many of the uses to which such tubes wereput, it did place serious limitations upon their utilization.

For instance, such tubes were of little or no value in circuits where itwas desired to use a tube to indicate a critical potential or to causethe operation of another device when a critical potential had beenreached. The present invention. may be used to construct tubes which areextremely simple in. their internal structure and, therefore, capableof. operation in the presence of and to withstand extremely large shocksup to and including over 35,000 gravities. Furthermore, tubes can bemade by our invention which will fire within .3 of a volt within thecritical potential in. temperature ranges between minus 40 degrees andplus 55 degrees C., and with a starting time of within 2 milli-seconds.

In the more limited aspects. of the invention, the-structure of thedevice is such. that the striking voltage may be regulated withincertain limits. Since the invention may be used in the construction ofso-called cold cathode types of tubes it is particularly desirable. forvoltage regulation or the other purposes to which it may be put, incircuits where current consumption is a critical limitation.

Still other advantages of.v the invention and the invention itself willbecome more apparent from the following description of some embodimentsthereof and which description is illustrated by the accompanyingdrawing.

In the drawings:

Fig. 1 is an enlarged view of a tube utilizing our invention withcertain parts broken away to provide a clearerillustration of partswhich would otherwise be hidden;

Fig. 2 is a diagrammatic view of a modified form of the invention;

Fig. 3 is a view of another embodiment of: our invention; and

Fig. 4 is a view of still another embodiment of our invention.

Throughout the drawings, like parts have been designated by likereference characters.

Referring now to Fig. 1, wherein there is a greatly enlargedillustration of a tube embodying the invention, as can be seen, itincludes a. glass envelope 10 having. a press 11 at the lower end,through which a. pair t lead-in wires. 12 and 13 extend. The lead-inwires extend into the glass envelope and the wire12 is. connected2,728,004 Patented Dec. 20, 1955 to onev ot the twosupport wires 14. Thetwo support wires. 14 each have. an inwardly bentcenter portion 15 whichis spot welded: toa cylindrical. cathode 17. The wires and cathode. maybe made of any suitable material such as nickel: The lower extremitiesof the wires 14 are disposed in. openings in a circular ceramic supportdisc 18 which extends inv close proximity to the envelope wall. One ofthe wires is bent at 14' to engage theunderside. of the. disc adjacent.the hole, and the point 12 of thelead-in wire. 12 where it is welded tothe other support. wire engages the ceramic disc adjacent the pointwhere the. support; wire goes through the disc.

The upper end of the cylinder 11 abuts a. mica disc 20 which rests onthe end of. the cylinder. The ends of the support wires 14 extendthrough the disc, and are. upset. at 22, to hold the disc securely inposition. The: mica disc, like. the. ceramicv disc, extends, close to:the envelope. wall- A. getter 23 is carried by the ends of the supportwires 14 in. such a position that, when it is flashed, the gettermaterial flashes against the upper end of the envelope.

The extremity oftheenvelope is shown with a tip 24 through which thetube may be evacuated and/0r filled with gas to the desired pressurebefore sealing oil.

A. center anode electrode 26 is provided which comprises a stiff Wire orrod extending coaxially with the cylindrical cathode, the end extendingthrough the ceramic support 18 and having welded thereto at 27 the leadwire 13.

, .A tube such as. this is usuallyfilled witha mixture of noble gases.Such a mixture could comprise. argon and neon at a pressure. of between10 and 30 mm. of mercury. The. amount. of neon gas; is normally smallbeing as little as 4 It will be appreciated that others of the noblegases may be used. and, that the proportions and pressure may vary; for.instance, a, mixture of 2% argon and 98% helium atv a pressure ofbetween and 100 mm. of, mercury is very satisfactory. The pressure ofthe gas to some degree determines the flash point or striking voltage.

As previously stated, a tube such as: has been described is commonlyknown as a glow tubeand when voltage.

of. a. suflicient amplitude. is applied, knownv as striking voltage,the: gas will become ionized. and conducting. During the time when it isconducting, it will maintain its. conductive state. at a considerablylower voltage than that needed to start it. Furthermore,, the startingvoltage varies throughouta wide range. Therefore, although the.regulation may be very good after it once starts, the variations in thestarting voltage seriously limits the uses to which it may be put.

Prior to the. invention, there. was no tube-of. this characteravailable. where. the striking, voltagev was always the: same or. withinreasonable limits of a predetermined value. Furthermore, the time of thestarting might vary. That is, if. a starting. voltage of volts wassutficient to start it within a fraction. of a second at one time,

this same voltage might not start it for several seconds.

at another time.

Among other things, prior glow tubes exhibited large and. variable darkcurrents in the region prior to and as the potential approached thebreakdown point. This.

caused a region of instability'as mentioned above.

We have. discovered that. this limitation on the striking; voltage maybe corrected by placing a source of energized particles such aselectrons or alpha particles in the tube. One materialv which. we havefound to be highly efiective is by welding: a small piece of metallicribbon 30havinga substance such, as radium impregnated therein to theanode. The radium emits alpha particles and high speed electrons. It.will be appreciated that this substance can be'placed anywhere in. thetube so long as a proper degree of ionization is produced at the pointof discharge.

We have found that a gold ribbon with a minute quantity of radiumtherein is extremely effective in its action and that a tube soconstructed and designed for a striking voltage of 120 volts will alwaysstrike Within .3 of a volt regardless of variations in ambienttemperature when the degree of ionization is satisfactory.

We also contemplate, and in some instances prefer, a substance such aspolonium which is essentially an alpha particle emitter. The use ofalpha particles for stabilizing the starting voltage is particularlydictated in places where beta and gamma rays are undesirable. It will beappreciated that a great many of the isotopes may be useful and in someinstances preferred, the principal limitation being that the half lifeof the material must be taken into consideration.

The reason that a tube embodying the invention can be stabilized toprovide a substantially exact starting voltage is because the radiationproduces a sufficient degree of ionization to cause the gas to breakdown at a predetermined voltage depending on'the various parameters ofthe tube. This is equivalent to saying that the tube is presensitized byproviding enough ions at the point of discharge that the addition of acritical potential gradient across the discharge point is sufiicient tocause the gas to break down, making it unnecessary for the addedpotential to provide the necessary ions before the breakdown potentialis reached. When the radio active material is apt to contaminate or haveany undesirable effect upon the other elements in the tube, it may becompletely enclosed such as by being placed in a bore 26a, as indicatedby the dotted lines, in the anode itself, thu permitting onlytheenergized particles to escape.

Such a tube may be connected into a circuit wherein when the potentialin the circuit reaches a predetermined maximum desired value, the tubewill strike causing a discharge of the circuit. With this type ofcircuit, the discharges which may succeed one another may be produced ata rate greater than that at which the circuit may build up succeedingpotentials. Thus, the discharge may also be used to indicate when thecritical potential is reached.

It has been commonly accepted theory that a tube,

of the character described as prior art, would discharge in the presenceof an ionizing event, such as the passage of a high speed electron oralpha particle between the discharge electrodes. This result has,according to accepted theory, been obtained at a result of the passageinto the device and between the electrodes of a cosmic ray. This haslargely been responsible for the inconsistencies in striking voltage,for, any one single event is not sufficient to produce the requireddegree of ionizatlon.

- In Fig. 2, there has been shown schematically another embodiment ofour invention wherein the anode 26 has the radio active material 30a inthe form of a flag disposed on a stem 31 that is welded to the anode at32. The cathode wall opposite to the flag is provided with a cup 33 inwhich a barium, cerium or magnesium compound 34 is disposed, and isadapted to be flashed, to provide a suitable cathode coating surface'onthe wall at 35 having the desired work function. r

In Fig. 3, there has been shown another embodiment of the invention. Inthis case, the usual glass envelope a is provided. A tube 40 of metal,such as nickelcobalt-iron, glass sealing alloy, of which there is one onthe market known as Kovar, extends through the press 11a and has securedto it at its upper end a pair of support rods 41 which may be welded tothe side of the tube. The supports 41 carry a cup 43, from the center ofwhich extends a rod 44 which comprises the anode. On the end of the rodis the ionizer 45 which may be constructed of any of the materialsspecified.

The tube is degassed and supplied with the ionizable gas through asecond tube 47 which may be of copper, although other metals may beemployed.

The cup 43 is provided with a material 43' of which a type having athermic action to release the material is desired and causes it to coatthe wall and form a cathode by evaporation. Such a'compound could be amixture including barium and/ or magnesium which, when flashed, causes ametallic layer to be deposited on the wall 48. A cathode rod 49 extendsinto the tube through the upper end and makes contact with the metalliclayer, thus forming the cathode and its connection.

The tube after being evacuated and degassed in the usual manner is thenflashed. After flashing, the ionizable gas such as argon and neon may beadmitted through the tubes 47 and 40 filling the tube to a pressureclose to but slightly lower than the desired pressure. The tube 47 isthen pinched off and sealed at 50.

The tube 47 may be pinched as indicated at 52, to change the pressure inthe tube until it is at the exact point where the desired strikingvoltage causes it to start.

One method of conditioning the tube contemplates filling the tube withgas to a lower pressure than that ultimately desired, applying a voltageto determine the striking voltage and then ultimately increasing thepressure and applying a voltage that will cause it to strike until thedesired pressure is reached at which it will strike at the desiredvoltage.

In Fig. 4, there is shown a greatly enlarged view of a glow tubemanufactured according to our invention. In this particular instance, itshould be mentioned that it is possible to manufacture glow tubesaccording to our invention that are of a very small size. For instance,the actual tube of Fig. 4 can be constructed A; of an inch in diameterand one inch long to provide an extremely rugged device capable ofwithstanding great shocks.

Referring to Fig. 4, the tube may comprise a cylindrical envelope 60 ofKovar or steel or other metal having a flange 61 at the lower end andbeing necked in slightly at 62. A sleeve 64 of magnesium is inserted inthe envelope, it being of a diameter to provide a good electricalcontact with the outer metal and forms the cathode. The upper end of thesleeve engages the shoulder 65 formed by the necked-in portion. Thelower end of the envelope is closed by a base which includes a shortcylinder 66 having a flange 67 adapted to be welded or soldered to theflange 61. The interior of the cylinder 66 is filled with glass 69 whichis fused to the cylinder and which glass supports the anode rod 70coaxially of the cylinder 60.

It will be seen that this structure allows for standardization in thetube structure and still enables certain changes to be made that willchange the operating range or striking potential of the tube. Forinstance, the magnesium sleeve could be in various thicknesses thuschanging the spacing between the electrodes; or other metals thanmagnesium, such as aluminum, barium, etc., may be used to provide acathode having the desired work function.

The upper surface of the bead may be provided with a circular flange 72extending upward and surrounding the anode.

The upper end of the anode carries a flag, or point 74, which may be ofmetal carrying the ionizing substance as previously indicated.

The reduced end 62 of the envelope has welded thereto a copper tube 75.This copper tube is adapted to be pinched off at 76 and sealed when thedesired pressure of gas is reached, or it may be sealed at the end asindicated at 77 and then deformed to increase the pressure as indicatedin connection with the description of Fig. 3.

It will therefore be seen that there has been discovered a means forestablishing a degree of ionization in the gas in a tube of thecharacter described whereby the striking voltage can be relied upon tobe effective within certain predetermined limits. This enables thedevice to be used in circuits where the striking voltage must beaccurately forecast. It also lends itself to uses where the device isused as a protective device that will definitely break down at apredetermined voltage and where a cold cathode type of device isdesirable.

Having thus described our invention, we are aware that numerous andextensive departures may be made therefrom without departing from thespirit or scope of the invention which is defined in the appendedclaims.

We claim:

1. The method of manufacture of a gas filled discharge device having acompressible tubulation, to predetermine the discharge point, whichcomprises filling the device with gas at a pressure below that requiredto cause discharge at a given potential and compressing the tubulationto reduce the volume of the chamber to increase the gas pressure in thetube until the desired striking voltage is attained.

2. The method of producing gas filled discharge devices having adistortable tube communicating with said device to provide a devicehaving a volume greater than that of the ultimate device which comprisesfilling the device with the desired gasto a pressure below that requiredfor the device to discharge at a predetermined voltage, applying avoltage to the device of a value which it is desired to cause the tubeto discharge, distorting said communicating tube to increase thepressure in the device to the point where the tube will discharge.

3. A glow discharge tube including a cylindrical metallic member, acathode sleeve disposed in said member in electrical contact therewithand formed of a material having the desired work function, said memberbeing formed with an outwardly extending base flange, a base for saidtube including a second cylindrical member having a flange disposed forengagement and sealed to said first flange, a glass bead filling saidmember and an anode supported thereby extending into the first memberand exteriorly of said tube, said bead being formed with a ringsurrounding said anode at the base thereof and in spaced relationthereto, and ionizer carried by said anode in the zone of dischargethereof, said first member being formed with a reduced tubular portionat the end opposite the base.

4. A gas discharge tube comprising a base member including a flangedsleeve and a glass to metal seal filling the sleeve, an anode comprisinga rigid rod carried by said glass seal, coaxial with the sleeve andextending upward therefrom, a cathode comprising a second flangedsleeve, said members being held in cooperative relation 1 to each otherby securing said sleeves together, and a sleeve of magnesium beingdisposed in closely sliding contact with said second sleeve inside saidsleeve.

5. A gas discharge tube including a cylindrical metallic member, acathode sleeve disposed in said member in electrical contact therewithand formed of a material having the desired work function, said memberbeing formed with an outwardly extending base flange, a base for saidtube including a second cylindrical member having a flange disposed forengagement and sealed to said first flange, a glass bead filling saidsecond member and an anode supported thereby extending into the firstmember and exteriorly of said tube and in spaced relation thereto, andan ionizer in the zone of discharge thereof.

6. An apparatus for causing a discharge between electrodes upon theapplicaion of a predetermined potential, including an envelope havingtwo or more electrodes for connection to the source of potential, anionizer disposed on one of the electrodes at the point of greatest fieldintensity, said envelope having therein a gas ionized by radio activedisintegration products of said ionizer to provide suflicient free ionsat the point of discharge to cause positive or definite striking at thedesired potential.

7. An apparatus as set forth in claim 6 wherein the disintegrationproducts comprise alpha particles.

8. An apparatus as set forth in claim 6 wherein the disintegrationproducts comprise beta particles.

9. An apparatus as set forth in claim 6 wherein the disintegrationproducts comprise gamma quanta.

10. An apparatus as set forth in claim 6 wherein the disintegrationproducts comprise alpha and beta particles and gamma quanta.

11. An apparatus of the class described including an envelope,electrodes in said envelope and a gas filling the envelope, one of saidelectrodes being provided with a longitudinally extending bore thereinand radium disposed in said bore.

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